1. Field of the Invention
The invention is concerned with a device, namely a screw press, for the production of oils by pressing and extracting an oleiferous raw material in the presence of a liquid extraction agent. The device includes an inlet for the raw material, a substantially cylindrical pressing body having outlets for oil and being connected to the inlet, and a press screw movably provided in the cylindrical pressing body. The press srew transports the raw material from the inlet into the pressing body and therefrom to a discharge outlet while pressing it.
For the purposes of the present specification and claims, the terms "oil" and "oleiferous" also refer to "fat" and "fatty" as well as to "extractable substances".
2. Description of Related Art
From DE-A-30 16 877, a process for the continuous separation of fat from organic raw materials is known wherein the raw materials are first shredded and optionally dried, then mashed using a fat dissolving agent and thereafter fed to a screw press.
Also, GB-A-1 340 484 is concerned with pressing in the presence of an extraction agent.
DE-C 665 873 refers to a process according to which an extraction agent is fed during pressing.
According to the process known from GB-A-1 340 484, palm oil may be produced by pressing the oleiferous fruit while adding a solvent to the material to be pressed under normal pressure at the intake of the press.
All known screw presses whereby oil is produced have the disadvantage in that their oil yields are not satisfactory.
Thus it is the object of the present invention to provide a screw press whereby the oleiferous raw material may be deoiled to an extent of 96-98%, based on the total oil content, in one single operation step.